Cancer pain and its impact on diagnosis, survival and quality of life

cGMP and cGMP-dependent protein kinase I pathway in dorsal root ganglia contributes to bone cancer pain in rats

STUDY DESIGN

A prospective, randomized experimental research.

OBJECTIVE

To demonstrate the role of cGMP (cyclic guanosine monophosphate)-cGKI (cGMP-dependent protein kinase I) pathway in dorsal root ganglia (DRG) in bone cancer pain.

SUMMARY OF BACKGROUND DATA

Treating bone cancer pain continues to possess a major clinical challenge because the specific cellular and molecular mechanisms underlying bone cancer pain remain elusive. cGMP and cGMP-dependent protein kinases pathway in DRG plays important role in nerve injury-induced hyperexcitability of DRG neurons, as well as neuropathic pain, however, whether this pathway participates in bone cancer pain is unknown.

METHODS

The rat model of bone cancer pain was produced by intramedullary injection of rat breast cancer cells (Walker 256) into right tibia. Thermal hyperalgesia and mechanical allodynia were measured before and after administration of inhibitor of cGMP-cGKs pathway (Rp-8-pCPT-cGMPS). Immunofluorescence and reverse transcription-polymerase chain reaction were used to reflect expression of cGKI in DRG neurons, whereas the concentration of cGMP in DRG was tested using enzyme-linked immunosorbent assay method. Whole-cell patch clamp was used to record the hyperexcitability of small neurons in DRG with or without cGKs inhibitor after tumor cell implantation (TCI).

RESULTS

TCI treatment significantly increased the concentration of cGMP in DRG and activity of cGKs in DRG and the spinal cord. TCI treatment also induced upregulation of cGKI messenger ribonucleic acid and protein in DRG, as well as enhanced hyperexcitability in DRG neurons. Spinal administration of Rp-8-pCPT-cGMPS, cGMP-cGKs inhibitor, significantly suppressed TCI-induced activation of cGMP-cGKI signaling, and hyperexcitability of DRG neurons. Meanwhile, in vivo intrathecal delivery of the Rp-8-pCPT-cGMPS significantly prevented and suppressed TCI-induced hyperalgesia and allodynia.

CONCLUSION

From these results, we confirm that TCI treatment activates cGMP-cGKI signaling pathway and continuing activation of this pathway in DRG is required for hyperalgesia and/or hyperalgesia and allodynia after TCI treatment.

LEVEL OF EVIDENCE

N/A.

Resveratrol attenuates bone cancer pain through the inhibition of spinal glial activation and CX3CR1 upregulation

The present study examined the effects of intrathecal use of resveratrol on pain hypersensitivities, spinal glia activation, and CX3CR1 expression in the model of bone cancer pain (BCP). The BCP model was established through intrathecally injecting Walker 256 mammary gland carcinoma cells to Sprague-Dawley rats. We found that spinal CX3CR1 expression and glial activation aggravated after inoculation. Resveratrol (i.t.) attenuated bone cancer-induced pain hypersensitivities, decreased CX3CR1 expression and glial activation in the spine in a BCP model. Resveratrol (i.t.) also attenuated mechanical allodynia resulting from intrathecally injecting fractalkine in rats. Inhibition of spinal glial activation and CX3CR1 upregulation may involve in resveratrol's analgesic effects. These findings demonstrated that resveratrol attenuated pain facilitation through inhibiting spinal glial activation and CX3CR1 upregulation in a BCP model.

Survival patterns in squamous cell carcinoma of the head and neck: pain as an independent prognostic factor for survival

Survival outcomes in patients with squamous cell carcinoma of the head and neck (HNSCC) vary by extent of disease, behavioral factors, and socioeconomic factors. We assessed the extent to which pretreatment pain influences survival in 2,340 newly diagnosed patients with HNSCC, adjusting for disease stage, symptoms, pain medications, comorbidities, smoking, alcohol consumption, age, sex, and race/ethnicity. Patients rated their pain at presentation to the cancer center (0 = "no pain" and 10 = "pain as bad as you can imagine"). Survival time was calculated from the date of diagnosis to the date of death of any cause or last follow-up. Five-year overall survival was calculated for all the variables assessed in the study. Severe pain (≥7) was most prevalent among those with oral cancer (20.4%; pharynx = 18.8%; larynx = 16.1%) and significantly varied by tumor stage, fatigue severity, smoking status, comorbid lung disease, and race (all P < .05) across cancer diagnoses. Overall 5-year survival varied by pain for oral (severe pain = 31% vs nonsevere pain = 52%; P < .001) and pharyngeal cancer (severe pain = 33% vs nonsevere pain = 53%; P < .001). Multivariable analyses showed that pain persisted as an independent prognostic factor for survival. Pain reported prior to treatment should be considered in understanding survival outcomes in HNSCC patients.

PERSPECTIVE

Pretreatment pain was an independent predictor of survival in a large sample of HNSCC patients even after accounting for tumor node metastasis stage, fatigue, age, race/ethnicity, smoking, and alcohol intake. Therefore, symptoms at presentation and before cancer treatment are important factors to be considered in understanding survival outcomes in HNSCC patients.

Bioclinical parameters driving decision-making of subsequent lines of treatment in metastatic castration-resistant prostate cancer

Different options are available as second-line treatment of metastatic castrate-resistant prostate cancer: cabazitaxel, abiraterone, and enzalutamide. Phase III studies evaluating cabazitaxel and the two hormonal agents have been shown to significantly prolong overall survival compared to mitoxantrone and placebo, respectively. Several studies have also demonstrated feasibility and activity of docetaxel rechallenge in case of a sufficient progression-free interval (3-6 months), good performance status, and previous acceptable safety profile, thus providing an additional treatment option in clinical practice. Clinical and biological parameters should be considered to tailor II line treatment. In clinical practice, we can primarily evaluate patients' fitness according to age, performance status, symptomatic disease, comorbidities, and expected safety profile of each drug. Different prognostic/predictive factors may be considered, such as presence of bone-limited or visceral metastases, length of androgen deprivation therapy (ADT) before chemotherapy, time to progression after docetaxel, Gleason score, PSA doubling time, and serum testosterone, even if their clinical relevance is still debated. This review will discuss current options of innovative drugs sequencing and selection according to bioclinical parameters.

Autocrine inhibition of the c-fms proto-oncogene reduces breast cancer bone metastasis assessed with in vivo dual-modality imaging

Breast cancer cells preferentially home to the bone microenvironment, which provides a unique niche with a network of multiple bidirectional communications between host and tumor, promoting survival and growth of bone metastases. In the bone microenvironment, the c-fms proto-oncogene that encodes for the CSF-1 receptor, along with CSF-1, serves as one critical cytokine/receptor pair, functioning in paracrine and autocrine fashion. Previous studies concentrated on the effect of inhibition of host (mouse) c-fms on bone metastasis, with resulting decrease in osteolysis and bone metastases as a paracrine effect. In this report, we assessed the role of c-fms inhibition within the tumor cells (autocrine effect) in the early establishment of breast cancer cells in bone and the effects of this early c-fms inhibition on subsequent bone metastases and destruction. This study exploited a multidisciplinary approach by employing two non-invasive, in vivo imaging methods to assess the progression of bone metastases and bone destruction, in addition to ex vivo analyses using RT-PCR and histopathology. Using a mouse model of bone homing human breast cancer cells, we showed that an early one-time application of anti-human c-fms antibody delayed growth of bone metastases and bone destruction for at least 31 days as quantitatively measured by bioluminescence imaging and computed tomography, compared to controls. Thus, neutralizing human c-fms in the breast cancer cell alone decreases extent of subsequent bone metastasis formation and osteolysis. Furthermore, we are the first to show that anti-c-fms antibodies can impact early establishment of breast cancer cells in bone.

Contributions of the host microenvironment to cancer-induced bone disease

The bone marrow provides a specialized and highly supportive microenvironment for tumor growth and development of the associated bone disease. It is a preferred site for breast and prostate cancer bone metastasis and the hematologic malignancy, multiple myeloma. For many years, researchers have focused upon the interactions between tumor cells and the cells directly responsible for bone remodeling, namely osteoclasts and osteoblasts. However, there is ever-increasing evidence for a multitude of ways in which the bone marrow microenvironment can promote disease pathogenesis, including via cancer-associated fibroblasts, the hematopoietic stem cell niche, myeloid-derived suppressor cells, and the sympathetic nervous system. This review discusses the recent advances in our understanding of the contribution of the host microenvironment to the development of cancer-induced bone disease.

Toll like receptor (TLR)-4 as a regulator of peripheral endogenous opioid-mediated analgesia in inflammation

BACKGROUND

Leukocytes containing opioid peptides locally control inflammatory pain. In the early phase of complete Freund's adjuvant (CFA)-induced hind paw inflammation, formyl peptides (derived e.g. from Mycobacterium butyricum) trigger the release of opioid peptides from neutrophils contributing to tonic basal antinociception. In the later phase we hypothesized that toll-like-receptor-(TLR)-4 activation of monocytes/macrophages triggers opioid peptide release and thereby stimulates peripheral opioid-dependent antinociception.

RESULTS

In Wistar rats with CFA hind paw inflammation in the later inflammatory phase (48-96 h) systemic leukocyte depletion by cyclophosphamide (CTX) or locally injected naloxone (NLX) further decreased mechanical and thermal nociceptive thresholds. In vitro β-endorphin (β-END) content increased during human monocyte differentiation as well as in anti-inflammatory CD14+CD16- or non-classical M2 macrophages. Monocytes expressing TLR4 dose-dependently released β-END after stimulation with lipopolysaccharide (LPS) dependent on intracellular calcium. Despite TLR4 expression proinflammatory M1 and anti-inflammatory M2 macrophages only secreted opioid peptides in response to ionomycin, a calcium ionophore. Intraplantar injection of LPS as a TLR4 agonist into the inflamed paw elicited an immediate opioid- and dose-dependent antinociception, which was blocked by TAK-242, a small-molecule inhibitor of TLR4, or by peripheral applied NLX. In the later phase LPS lowered mechanical and thermal nociceptive thresholds. Furthermore, local peripheral TLR4 blockade worsened thermal and mechanical nociceptive pain thresholds in CFA inflammation.

CONCLUSION

Endogenous opioids from monocytes/macrophages mediate endogenous antinociception in the late phase of inflammation. Peripheral TLR4 stimulation acts as a transient counter-regulatory mechanism for inflammatory pain in vivo, and increases the release of opioid peptides from monocytes in vitro. TLR4 antagonists as new treatments for sepsis and neuropathic pain might unexpectedly transiently enhance pain by impairing peripheral opioid analgesia.

IL-4, JAK-STAT signaling, and pain

During inflammation, several mediators directly or indirectly induce pain including pro-inflammatory cytokines and there is evidence that the JAK-STAT pathway is involved in the formation of pronociceptive cytokines. The same pathway, however, is also of importance for anti-inflammatory cytokines such as IL-4 to counteract the inflammatory reaction and-as it seems based on the current literature-nociceptive symptoms. Current therapeutic approaches targeting molecules of the JAK-STAT signaling cascade are auspicious but as this review demonstrates, more experimental and clinical studies are required to decipher the specific contribution of this pathway in the modulation of pain.

Characteristics and Quality of Life in Gynecologic Cancer Patients with Chemotherapy-induced Peripheral Neuropathy

PURPOSE

The purpose of this study was to identify chemotherapy induced peripheral neuropathy, quality of life of patients with gynecologic cancer.

METHODS

This was a cross-sectional survey design. We collected 130 patients with gynecologic cancer. They complete a self reported questionnaire including items related neuropathy and quality of life (FACT-GOG/Ntx subscale, FACT-G scale).

RESULTS

The neuropathy score was 14.3+/-7.9. The quality of life score was 64.8+/-16.4. The neuropathy induced significant difference according to diabetic status, difficulties in performing household chores and willing to discontinuity of chemotherapy. And duration of cancer diagnosis, neuropathy, number of total chemo agent associated with quality of life. There was a negative correlation between number of total chemo agent and quality of life. Neuropathy independently affected quality of life.

CONCLUSION

Chemotherapy induced peripheral neuropathy of patients with gynecologic cancer adversely affected women's quality of life and activities of daily living. To improve patient's quality of life, it is important that accurate assess and appropriately manage neuropathy in patients with gynecologic cancer.

Genome-wide identification and functional analyses of microRNA signatures associated with cancer pain

Cancer pain remains a major challenge and there is an urgent demand for the development of specific mechanism-based therapies. Various diseases are associated with unique signatures of expression of microRNAs (miRNAs), which reveal deep insights into disease pathology. Using a comprehensive approach combining genome-wide miRNA screening, molecular and in silico analyses with behavioural approaches in a clinically relevant model of metastatic bone-cancer pain in mice, we now show that tumour-induced conditions are associated with a marked dysregulation of 57 miRNAs in sensory neurons corresponding to tumour-affected areas. By establishing protocols for interference with disease-induced miRNA dysregulation in peripheral sensory neurons in vivo, we functionally validate six dysregulated miRNAs as significant modulators of tumour-associated hypersensitivity. In silico analyses revealed that their predicted targets include key pain-related genes and we identified Clcn3, a gene encoding a chloride channel, as a key miRNA target in sensory neurons, which is functionally important in tumour-induced nociceptive hypersensitivity in vivo. Our results provide new insights into endogenous gene regulatory mechanisms in cancer pain and open up attractive and viable therapeutic options.

Analgesic efficacy and mode of action of a selective small molecule angiotensin II type 2 receptor antagonist in a rat model of prostate cancer-induced bone pain

OBJECTIVE

The pathobiology of prostate cancer (PCa)-induced bone pain (PCIBP) has both inflammatory and neuropathic components. Previously, we showed that small molecule angiotensin II type 2 receptor (AT2 R) antagonists with >1,000-fold selectivity over the angiotensin II type 1 receptor produced dose-dependent analgesia in a rat model of neuropathic pain. Here, we assessed the analgesic efficacy and mode of action of the AT2 R antagonist, EMA200, in a rat model of PCIBP.

METHODS

At 14-21 days after unilateral intratibial injection of AT3B PCa cells, rats exhibiting hindpaw hypersensitivity received single intravenous bolus doses of EMA200 (0.3-10 mg/kg) or vehicle, and analgesic efficacy was assessed. The mode of action was investigated using immunohistochemical, Western blot, and/or molecular biological methods in lumbar dorsal root ganglia (DRGs) removed from drug-naïve and EMA200-treated PCIBP rats relative to sham-control rats.

RESULTS

Intravenous bolus doses of EMA200 produced dose-dependent analgesia in PCIBP rats. Lumbar DRG levels of angiotensin II, nerve growth factor (NGF), tyrosine kinase A (TrkA), phospho-p38 mitogen-activated protein kinase (MAPK), and phospho-p44/p42 MAPK, but not the AT2 R, were increased significantly (P < 0.05) in PCIBP rats, c.f. the corresponding levels for sham controls. EMA200 produced analgesia in PCIBP rats by reducing elevated angiotensin II levels in the lumbar DRGs to attenuate augmented angiotensin II/AT2 R signaling. This in turn reduced augmented NGF/TrkA signaling in the lumbar DRGs. The net result was inhibition of p38 MAPK and p44/p42 MAPK activation.

CONCLUSION

Small molecule AT2 R antagonists are worthy of further investigation as novel analgesics for relief of intractable PCIBP and other pain types where hyperalgesia worsens symptoms.

Transcriptional mechanisms underlying sensitization of peripheral sensory neurons by granulocyte-/granulocyte-macrophage colony stimulating factors

BACKGROUND

Cancer-associated pain is a major cause of poor quality of life in cancer patients and is frequently resistant to conventional therapy. Recent studies indicate that some hematopoietic growth factors, namely granulocyte macrophage colony stimulating factor (GMCSF) and granulocyte colony stimulating factor (GCSF), are abundantly released in the tumor microenvironment and play a key role in regulating tumor-nerve interactions and tumor-associated pain by activating receptors on dorsal root ganglion (DRG) neurons. Moreover, these hematopoietic factors have been highly implicated in postsurgical pain, inflammatory pain and osteoarthritic pain. However, the molecular mechanisms via which G-/GMCSF bring about nociceptive sensitization and elicit pain are not known.

RESULTS

In order to elucidate G-/GMCSF mediated transcriptional changes in the sensory neurons, we performed a comprehensive, genome-wide analysis of changes in the transcriptome of DRG neurons brought about by exposure to GMCSF or GCSF. We present complete information on regulated genes and validated profiling analyses and report novel regulatory networks and interaction maps revealed by detailed bioinformatics analyses. Amongst these, we validate calpain 2, matrix metalloproteinase 9 (MMP9) and a RhoGTPase Rac1 as well as Tumor necrosis factor alpha (TNFα) as transcriptional targets of G-/GMCSF and demonstrate the importance of MMP9 and Rac1 in GMCSF-induced nociceptor sensitization.

CONCLUSION

With integrative approach of bioinformatics, in vivo pharmacology and behavioral analyses, our results not only indicate that transcriptional control by G-/GMCSF signaling regulates a variety of established pain modulators, but also uncover a large number of novel targets, paving the way for translational analyses in the context of pain disorders.

Opioid requirement, opioid receptor expression, and clinical outcomes in patients with advanced prostate cancer

BACKGROUND

Preclinical studies show that opioids stimulate angiogenesis and tumor progression through the mu opioid receptor (MOR). Although MOR is overexpressed in several human malignancies, the effect of chronic opioid requirement on cancer progression or survival has not been examined in humans.

METHODS

We performed a retrospective analysis on 113 patients identified in the Minneapolis VA Tumor Registry (test cohort) and 480 patients from the national VA Central Cancer Registry (validation cohort) who had been diagnosed with stage IV prostate cancer between 1995 and 2010 to examine whether MOR expression or opioid requirement is associated with disease progression and survival. All opioids were converted to oral morphine equivalents for comparison. Laser scanning confocal microscopy was used to analyze MOR immunoreactivity in prostate cancer biopsies. The effects of variables on outcomes were analyzed in univariable and multivariable models.

RESULTS

In patients with metastatic prostate cancer, MOR expression and opioid requirement were independently associated with inferior progression-free survival (hazard ratio [HR] 1.65, 95% confidence interval [CI] 1.33-2.07, P<.001 and HR 1.08, 95% CI 1.03-1.13, P<.001, respectively) and overall survival (HR 1.55, 95% CI 1.20-1.99, P<.001 and HR 1.05, 95% CI 1.00-1.10, P = .031, respectively). The validation cohort confirmed that increasing opioid requirement was associated with worse overall survival (HR 1.005, 95% CI 1.002-1.008, P = .001).

CONCLUSION

Higher MOR expression and greater opioid requirement are associated with shorter progression-free survival and overall survival in patients with metastatic prostate cancer. Nevertheless, clinical practice should not be changed until prospective randomized trials show that opioid use is associated with inferior clinical outcomes, and that abrogation of the peripheral activities of opioids ameliorates this effect.

Impairment-driven cancer rehabilitation: an essential component of quality care and survivorship

Adult cancer survivors suffer an extremely diverse and complex set of impairments, affecting virtually every organ system. Both physical and psychological impairments may contribute to a decreased health-related quality of life and should be identified throughout the care continuum. Recent evidence suggests that more cancer survivors have a reduced health-related quality of life as a result of physical impairments than due to psychological ones. Research has also demonstrated that the majority of cancer survivors will have significant impairments and that these often go undetected and/or untreated, and consequently may result in disability. Furthermore, physical disability is a leading cause of distress in this population. The scientific literature has shown that rehabilitation improves pain, function, and quality of life in cancer survivors. In fact, rehabilitation efforts can ameliorate physical (including cognitive) impairments at every stage along the course of treatment. This includes prehabilitation before cancer treatment commences and multimodal interdisciplinary rehabilitation during and after acute cancer treatment. Rehabilitation appears to be cost-effective and may reduce both direct and indirect health care costs, thereby reducing the enormous financial burden of cancer. Therefore, it is critical that survivors are screened for both psychological and physical impairments and then referred appropriately to trained rehabilitation health care professionals. This review suggests an impairment-driven cancer rehabilitation model that includes screening and treating impairments all along the care continuum in order to minimize disability and maximize quality of life.

The development of chronic pain: physiological CHANGE necessitates a multidisciplinary approach to treatment

Chronic pain is currently under-diagnosed and under-treated, partly because doctors' training in pain management is often inadequate. This situation looks certain to become worse with the rapidly increasing elderly population unless there is a wider adoption of best pain management practice. This paper reviews current knowledge of the development of chronic pain and the multidisciplinary team approach to pain therapy. The individual topics covered include nociceptive and neuropathic pain, peripheral sensitization, central sensitization, the definition and diagnosis of chronic pain, the biopsychosocial model of pain and the multidisciplinary approach to pain management. This last section includes an example of the implementation of a multidisciplinary approach in Belgium and describes the various benefits it offers; for example, the early multidimensional diagnosis of chronic pain and rapid initiation of evidence-based therapy based on an individual treatment plan. The patient also receives continuity of care, while pain relief is accompanied by improvements in physical functioning, quality of life and emotional stress. Other benefits include decreases in catastrophizing, self-reported patient disability, and depression. Improved training in pain management is clearly needed, starting with the undergraduate medical curriculum, and this review is intended to encourage further study by those who manage patients with chronic pain.

The role of morphine in animal models of human cancer: does morphine promote or inhibit the tumor growth?

Morphine, a highly potent analgesic agent, is widely used to relieve pain and suffering of patients with cancer. Additionally, it has been reported that morphine is important in the regulation of cancerous tissue. Morphine relieves pain by acting directly on the central nervous system, although its activities on peripheral tissues are responsible for many adverse side effects. For these reasons, it is very important also to understand the role of morphine in cancer treatment. The published literature reporting the effect of morphine on tumor growth presents some discrepancies, with reports suggesting that morphine may either promote or inhibit the tumor growth. It has been also demonstrated that morphine modulates angiogenesis which is important for primary tumour growth, invasiveness, and the development of metastasis. This review will focus on the latest findings on the role of morphine in the regulation of cancer cell growth and angiogenesis.

Spiritual therapy to improve the spiritual well-being of Iranian women with breast cancer: a randomized controlled trial

Purpose. The aim of this study was to investigate the role of spiritual therapy intervention in improving the spiritual well-being and quality of life (QOL) of Iranian women with breast cancer. Methods. This randomized controlled clinical trial (RCT) recruited 65 women with breast cancer, randomly assigned to a 6-week spirituality-based intervention (n = 34) or control group (n = 31). Before and after six-week spiritual therapy intervention, spiritual well-being and quality of life (QOL) were assessed using Functional Assessment of Chronic Illness Therapy Spiritual Well-being scale (FACIT-Sp12) and cancer quality-of-life questionnaire (QLQ-C30), respectively. t-test, Paired t-test, pearson's correlation, and hierarchical regression analyses were used for analysis using Predictive Analytic software (PASW, version 18) for Windows. Results. After six spiritual therapy sessions, the mean spiritual well-being score from 29.76 (SD = 6.63) to 37.24 (SD = 3.52) in the intervention group (P < 0.001). There was a significant difference between arms of study (F = 22.91, P < 0.001). A significant positive correlation was detected between meaning and peace with all subscales of functional subscales on European Organization for Research and Treatment of Cancer quality of Life (EORTC QLQ-C30) (P < 0.05). Hierarchical regression analyses of participants indicated that the study arm, pain, and financial impact were significant predictors of spiritual well-being and overall QOL. Social functioning was another significant predictor of spiritual well-being. Conclusion. The results of this randomized controlled trial study suggest that participation in spiritual therapy program is associated with improvements in spiritual well-being and QOL. Targeted interventions to acknowledge and incorporate spiritual needs into conventional treatment should be considered in caring of Iranian patients with breast cancer.

Pathobiology and management of prostate cancer-induced bone pain: recent insights and future treatments

Prostate cancer (PCa) has a high propensity for metastasis to bone. Despite the availability of multiple treatment options for relief of PCa-induced bone pain (PCIBP), satisfactory relief of intractable pain in patients with advanced bony metastases is challenging for the clinicians because currently available analgesic drugs are often limited by poor efficacy and/or dose-limiting side effects. Rodent models developed in the past decade show that the pathobiology of PCIBP comprises elements of inflammatory, neuropathic and ischemic pain arising from ectopic sprouting and sensitization of sensory nerve fibres within PCa-invaded bones. In addition, at the cellular level, PCIBP is underpinned by dynamic cross talk between metastatic PCa cells, cellular components of the bone matrix, factors associated with the bone microenvironment as well as peripheral components of the somatosensory system. These insights are aligned with the clinical management of PCIBP involving use of a multimodal treatment approach comprising analgesic agents (opioids, NSAIDs), radiotherapy, radioisotopes, cancer chemotherapy agents and bisphosphonates. However, a major drawback of most rodent models of PCIBP is their short-term applicability due to ethical concerns. Thus, it has been difficult to gain insight into the mal(adaptive) neuroplastic changes occurring at multiple levels of the somatosensory system that likely contribute to intractable pain at the advanced stages of metastatic disease. Specifically, the functional responsiveness of noxious circuitry as well as the neurochemical signature of a broad array of pro-hyperalgesic mediators in the dorsal root ganglia and spinal cord of rodent models of PCIBP is relatively poorly characterized. Hence, recent work from our laboratory to develop a protocol for an optimized rat model of PCIBP will enable these knowledge gaps to be addressed as well as identification of novel targets for drug discovery programs aimed at producing new analgesics for the improved relief of intractable PCIBP.

Protease-activated receptor 2 in dorsal root ganglion contributes to peripheral sensitization of bone cancer pain

BACKGROUND

Treating bone cancer pain continues to be a major clinical challenge, and the underlying mechanisms of bone cancer pain remain elusive. Protease-activated receptor 2 (PAR2) has been reported to be involved in neurogenic inflammation, nociceptive pain and hyperalgesia. Here, we investigated the role of PAR2 in bone cancer pain development.

METHORDS

Expression of PAR2, mechanical allodynia, thermal hyperalgesia and neurochemical alterations induced by bone cancer pain were analysed in male, adult C3H/HeJ mice with tumour cell implantation (TCI). To investigate the contribution of PAR2 to bone cancer pain, PAR2 antagonist peptide and PAR2 knockout mice were used.

RESULTS

TCI produced bone cancer-related pain behaviours. Production and persistence of these pain behaviours were well correlated with TCI-induced up-regulation of PAR2 in sciatic nerve and dorsal root ganglia (DRG). PAR2 knockout and spinal administration of PAR2 antagonist peptide prevented and/or reversed bone cancer-related pain behaviours and associated neurochemical changes in DRG and dorsal horn (DH). TCI also induced proteases release in tumour-bearing tibia, sciatic nerve and DRG. Plantar injection of supernatant from sarcoma cells induced PAR2 up-regulation and intracellular calcium [Ca(2+) ]i increase in DRG, and calcitonin gene-related peptide accumulation in DH, as well as significant thermal and mechanical hyperalgesia, which were all in PAR2-dependent manners.

CONCLUSION

These findings suggest that PAR2 may be a key mediator for peripheral sensitization of bone cancer pain. Inhibiting PAR2 activation, especially during the early phase, may be a new therapy for preventing/suppressing development of bone cancer pain.

Chemotherapy-Induced Peripheral Neuropathy in Pediatric Cancer Patients

Chemotherapy-induced peripheral neuropathies (CIPNs) are an increasingly common neuropathic and pain syndrome in adult and pediatric cancer patients and survivors [1-69]. However, symptoms associated with CIPNs are often undiagnosed, under-assessed, and communications problems between clinicians, family members, and patients have been observed [70-73]. Less is known about the prevalence and impact of CIPNs on pediatric cancer populations [70-71]. This article aims to provide a brief understanding of CIPNs in pediatric populations, and to review the evidence for both its prevention and treatment.

Changes in protein expression and distribution of spinal CCR2 in a rat model of bone cancer pain

Accumulating evidence suggests that chemokine C-C motif receptor 2 (CCR2) plays an important role in neuropathic pain. It has been shown that spinal CCR2 is upregulated in several neuropathic pain models and expressed by neuronal and glial cells in the spinal cord. In this study, we investigated the expression changes and cellular localization of spinal CCR2 in a rat model of bone cancer induced by Walker 256 cell inoculation. The present results indicated that mechanical allodynia progressively increased in bone cancer pain (BCP) rats. Western blot and immunohistochemical analysis demonstrated that the expression of CCR2 in the spinal cord was significantly increased on day 6, 12, and 18 in BCP rats, with a peak on day 6. Furthermore, double immunofluorescence labeling indicated that CCR2 was expressed by both microglia and neurons in the spinal cord. These results suggest that CCR2 may be involved in the development of BCP, and that targeting CCR2 may be a new strategy for the treatment of BCP.

Pain, movement, and mind: does physical activity mediate the relationship between pain and mental health among survivors of breast cancer?

OBJECTIVES

This study examined the relationship between pain and mental health outcomes of depression and affect among survivors of breast cancer. The mediating role of physical activity was also tested.

METHODS

Survivors of breast cancer (N=145) completed self-report measures of pain symptoms at baseline, wore an accelerometer for 7 days, and reported levels of depression symptoms and negative and positive affect 3 months later. Hierarchical linear regression analyses, controlling for personal and cancer-related demographics, were used to test the association between pain symptoms and each mental health outcome, as well as the mediation effect of physical activity.

RESULTS

Pain positively predicted depression symptoms [F(6,139)=4.31, P<0.01, R=0.15] and negative affect [F(5,140)=4.17, P<0.01, R=0.13], and negatively predicted positive affect [F(6,139)=2.12, P=0.03, R=0.08]. Physical activity was a significant (P<0.01) partial mediator of the relationship between pain and depression and between pain and positive affect.

DISCUSSION

Participation in physical activity is one pathway through which pain influences mental health. Efforts are needed to help survivors of breast cancer manage pain symptoms and increase their level of physical activity to help improve mental health.

Enhanced SCN7A/Nax expression contributes to bone cancer pain by increasing excitability of neurons in dorsal root ganglion

Bone pain is one of the most common complications in cancer patients with bone metastases, and has the most significant impact on quality of life for patients. Patients with bone cancer pain may be difficult to treat due to the poor understanding of the mechanisms; therefore, the mechanisms of bone cancer pain required elucidation for developing new therapeutics. Recent studies show that SCN7A/Nax channel serves as a sodium-level sensor of the body fluid that controls the Na-intake behavior by changing the excitability of neurons. In the current study, the expression of SCN7A/Nax and the excitability of primary sensory neurons in bone cancer pain rats were examined. The analgesic effects of knockdown SCN7A/Nax channel using RNAi lentivirus intrathecal treatment were evaluated with a behavioral test. The results showed that implantation of sarcoma induced ongoing and movement-evoked pain behaviors, whereas SCN7A/Nax knockdown prevented the onset of these hyperalgesia. Immunohistochemistry showed that SCN7A/Nax was located in the medium- to large-sized neurons in dorsal root ganglions (DRGs). The proportion of SCN7A/Nax-positive cells was significantly increased in DRGs ipsilateral to sarcoma implantation. Immunostaining results were further confirmed by Western blot and real time-polymerase chain reaction (RT-PCR) analyses. Recording from primary sensory neurons in excised rat dorsal root ganglias, we found that most of SCN7A/Nax-positive neurons exhibited subthreshold oscillations, depolarized resting membrane potential and more negative threshold of action potential. These electrophysiological changes of neurons increased ectopic spike discharge which was thought to be an important generator of chronic pain, however, the hyperexcitability was completely reversed by SCN7A/Nax knockdown. These results demonstrate that enhanced expression of SCN7A/Nax channel within distinct subpopulation of DRG neurons contributes to bone cancer pain by increasing the excitability of these neurons. These findings may lead to novel strategies for the treatment of bone cancer pain.

Fentanyl decreases discharges of C and A nociceptors to suprathreshold mechanical stimulation in chronic inflammation

An essential component of mechanical hyperalgesia resulting from tissue injury is an enhanced excitability of nociceptive neurons, termed mechanical sensitization. Local application of opioids to inflamed rat paws attenuates mechanical hyperalgesia and reduces electrical excitability of C-fiber nociceptors in acute injury. Here, we examined the effects of the opioid receptor agonist fentanyl on the mechanical coding properties of not only C- but also A-fiber nociceptors innervating the rat hind paw in a model of chronic pain, i.e., 4 days after Freund's complete adjuvant-induced inflammation. The peripheral mechanosensitive terminals of C-fibers (n = 143), A-fibers (n = 79), and low-threshold mechanoreceptors (n = 25) were characterized using the in vitro skin-nerve preparation from the saphenous nerve. Although mechanical activation thresholds were not changed, discharges to suprathreshold mechanical stimuli were elevated significantly in both A- and C-fiber nociceptors from inflamed tissue. In addition, the proportion of nociceptors as well as the frequency of spontaneous discharges in A (14% vs. 0%)- and C (28% vs. 8%)-fibers were increased in inflamed compared with normal tissue. Fentanyl inhibited responses to suprathreshold stimuli in a significantly higher proportion of not only C (36% vs. 7%)- but also A (41% vs. 8%)-fibers in inflamed tissue in a naloxone-reversible and concentration-dependent manner. Our results demonstrate that mechanical sensitization persists in chronic inflammation, in correlation with behavioral hyperalgesia. Opioid sensitivity of both A- and C-fibers is markedly augmented. This is consistent with an upregulation or enhanced functionality of opioid receptors located at the peripheral terminals of sensitized nociceptors.

Incidence of severe pain in newly diagnosed ambulatory patients with stage IV cancer

BACKGROUND

Pain is common among cancer patients.

OBJECTIVE

To characterize the incidence of severe pain among newly diagnosed patients with stage IV cancer in ambulatory care.

METHODS

A retrospective cohort of 505 ambulatory oncology patients with newly diagnosed stage IV solid tumours at a comprehensive cancer centre (Dana-Farber Cancer Institute, Boston, Massachusetts, USA) was followed from January 1, 2004, to December 31, 2006. Pain intensity scores were extracted from electronic medical records. The incidence of severe pain was calculated using the maximum monthly pain scores reported at outpatient visits.

RESULTS

Of the 505 patients included in the present study, 340 (67.3%) were pain-free at the initial visit, 90 (17.8%) experienced mild pain, 48 (9.5%) experienced moderate pain and 27 (5.4%) experienced severe pain. At least one episode of severe pain within one year of diagnosis was reported by 29.1% of patients. Patients with head and neck, gastrointestinal and thoracic malignancies were more likely to experience severe pain compared with patients with other types of cancer (52.6%, 33.9% and 30.5%, respectively). In the multivariable model, patients whose primary language was not English (OR 2.90 [95% CI 1.08 to 7.80]), patients who reported severe pain at the initial visit (OR 9.30 [95% CI 3.72 to 23.23]) and patients with head and neck (OR 10.17 [95% CI 2.87 to 36.00]) or gastrointestinal (OR 4.05 [95% CI 1.23 to 13.35]) cancers were more likely to report severe pain in the following year.

CONCLUSIONS

The incidence of severe pain was high in ambulatory patients with newly diagnosed stage IV cancer.

Comparative responsiveness of pain measures in cancer patients

Brief measures to assess and monitor pain in cancer patients are available, but few head-to-head psychometric comparisons of different measures have been reported. Baseline and 3-month data were analyzed from 274 patients enrolled in the Indiana Cancer Pain and Depression (INCPAD) trial. Participants completed the Brief Pain Inventory (BPI), the PEG (a 3-item abbreviated version of the BPI), the short form (SF)-36 pain scale, and a pain global rating of change measure. The global rating was used as the criterion for standardized response mean and receiver operating characteristic curve analyses. To assess responsiveness to the trial intervention, we evaluated standardized effect size statistics stratified by trial arm. All measures were responsive to global improvement, discriminated between participants with and without improvement, and detected a significant intervention treatment effect. Short and longer measures were similarly responsive. Also, composite measures that combined pain severity and interference into a single score (BPI total, PEG, SF-36 pain) performed comparably to separate measures of each domain (BPI severity and BPI interference).

PERSPECTIVE

Pain measures as brief as 2 or 3 items that provide a single score are responsive in patients with cancer-related pain. Ultra-brief measures offer a valid and efficient means of assessing and monitoring pain for the clinical management as well as research of cancer-related pain.

Impairment of long-term depression in the anterior cingulate cortex of mice with bone cancer pain

The anterior cingulate cortex (ACC) has been shown to play an important role in pain-related perception and chronic pain. However, little is known about the molecular mechanisms involved. To address this issue, we analyzed excitatory synaptic transmission and long-term synaptic plasticity in layer II/III pyramidal neurons within the rostral ACC (rACC) from mice with bone cancer pain induced by intra-tibia implantation of osteolytic fibrosarcoma cells. Ex vivo whole-cell patch-clamp recordings from rACC neurons showed no significant alterations in presynaptic glutamate release probability and postsynaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated synaptic responses in mice with bone cancer pain. However, mechanical allodynia occurred in conjunction with decreased N-methyl-d-aspartate (NMDA)/AMPA ratio of synaptic currents elicited in bilateral rACC neurons. In addition, the induction of NMDA receptor-dependent long-term depression (LTD) at rACC synapses was impaired in rACC neurons of tumor-bearing mice. Western blot analysis revealed a significant decrease in the levels of NR1, NR2A, and NR2B subunits of NMDA receptors in the rACC under bone cancer pain condition. No significant changes in overall mRNA levels for any of the NMDA receptor subunits or calpain activity were observed in the rACC of tumor-bearing mice. These results indicate that tumor-induced injury or remodeling of primary afferent sensory nerve fibers that innervate the tumor-bearing bone may cause a persistent decrease in NMDA receptor expression in rACC neurons, resulting in a loss of LTD induction, thereby leading to long-term alterations of rACC activity and creating exaggerated pain behaviors.

Predictors of cancer-related pain improvement over time

OBJECTIVE

To determine the predictors of pain improvement among patients being treated for cancer-related pain over 12 months.

METHODS

A secondary analysis of the telephone care Indiana Cancer Pain and Depression trial was performed. Patients (n = 274) were interviewed at baseline and after 1, 3, 6, and 12 months. Pain improvement outcomes included both a continuous measure (Brief Pain Inventory score) and a categorical measure (pain improved versus pain not improved). Predictor variables included change in depression, age, sex, race, marital status, socioeconomic disadvantage, medical comorbidity, type of cancer, and phase of cancer. Multivariable repeated measures were conducted, adjusting for intervention group assignment, baseline pain severity, and time in months since baseline assessment.

RESULTS

Factors significantly predicting both continuous and categorical pain improvement included participating in the intervention group (β = -0.92, p < .001, odds ratio [OR] = 2.53, 95% confidence interval [CI] = 1.65-3.89), greater improvement in depression (β = -0.31, p = .003, OR = 1.84, 95% CI = 1.35-2.51), higher socioeconomic status (Socioeconomic Disadvantage index; β = 0.25, p = .034; OR = 0.73, 95% CI = 0.56-0.94), and fewer comorbid conditions (β = 0.20, p = .002; OR = 0.84, 95% CI = 0.73-0.96). Patients with more severe pain at baseline or with recurrent or progressive cancer were less likely to experience continuous or categorical pain improvement, respectively.

CONCLUSIONS

Effective management of depression and comorbid conditions along with improvement of social services could be critical components of a comprehensive pain management. Patients with more severe pain or with recurrent or progressive cancers may require closer monitoring and adequate treatment of pain. Trial Registration clinicaltrials.gov Identifier: NCT00313573.

SNPs in PTGS2 and LTA predict pain and quality of life in long term lung cancer survivors

PURPOSE

Lung cancer survivors report the lowest quality of life relative to other cancer survivors. Pain is one of the most devastating, persistent, and incapacitating symptoms for lung cancer survivors. Prevalence rates vary with 80-100% of survivors experiencing cancer pain and healthcare costs are five times higher in cancer survivors with uncontrolled pain. Cancer pain often has a considerable impact on quality of life among cancer patients and cancer survivors. Therefore, early identification, and treatment is important. Although recent studies have suggested a relationship between single nucleotide polymorphisms (SNPs) in several cytokine and inflammation genes with cancer prognosis, associations with cancer pain are not clear. Therefore, the primary aim of this study was to identify SNPs related to pain in lung cancer survivors.

PATIENTS AND METHODS

Participants were enrolled in the Mayo Clinic Lung Cancer Cohort upon diagnosis of their lung cancer. 1149 Caucasian lung cancer survivors (440 surviving <3 years; 354 surviving 3-5 years; and 355 surviving >5 years) completed study questionnaires and had blood DNA samples available. Ten SNPS from PTGS2 and LTA genes were selected based on the serum-based studies in the literature. Outcomes included pain, and quality of life as measured by the SF-8.

RESULTS

Of the 10 SNPs evaluated in LTA and PTGS2 genes, 3 were associated with pain severity (rs5277; rs1799964), social function (rs5277) and mental health (rs5275). These results suggested both specificity and consistency of these inflammatory gene SNPs in predicting pain severity in lung cancer survivors.

CONCLUSION

These results provide support for genetic predisposition to pain severity and may aid in identification of lung cancer survivors at high risk for morbidity and poor QOL.

Activation of c-jun N-terminal kinase in spinal cord contributes to breast cancer induced bone pain in rats

BACKGROUND

The most frequent pain in patients with metastatic breast and prostate cancer is bone pain, which can be severe and difficult to treat. The mechanisms underlying this pain remain unclear. Here we investigated the role of c-jun N-terminal kinase (JNK) pathway in the spinal cord in cancer-induced bone pain (CIBP).

RESULTS

In this study, we used an established rat CIBP model to investigate the possible role of JNK activation in the spinal cord. After intra-tibial inoculation with Walker 256 rat mammary gland carcinoma cells, the rats displayed mechanical allodynia on day 5, which lasted to day 16. The activation of JNK in neurons and astrocytes in the spinal cord was found on day 12 and day 16 after intra-tibial inoculation with carcinoma cells. A single intrathecal injection with JNK inhibitor SP600125 by lumbar puncture attenuated mechanical allodynia on day 12, and repeated intrathecal injection of SP600126 from day 10 to day 14 had a cumulative analgesic effect on CIBP.

CONCLUSIONS

Taken together, our results demonstrated for the first time that JNK activation in the spinal cord is required in the maintenance of CIBP. Inhibition of the spinal JNK pathway may provide a new therapy for CIBP management.

Pathophysiology and medical treatment of pain in fibrous dysplasia of bone

One of the most common complications of fibrous dysplasia of bone (FD) is bone pain. Usual pain killers are often of inadequate efficacy to control this bone pain. The mechanism of bone pain in FD remains uncertain, but by analogy with bone tumors one may consider that ectopic sprouting and formation of neuroma-like structures by sensory and sympathetic nerve fibers also occur in the dysplastic skeleton. Bone pain has been reported in up to 81% of adults and 49% of children. It affects predominantly the lower limbs and the spine. The degree of pain is highly variable and adults reports more pain than children. Bisphosphonates have been shown to reduce bone pain in uncontrolled studies. Their influence on bone strength remains unknown. In a randomized trial testing alendronate, bone pain was not significantly improved. Another trial assessing the effect of risedronate is ongoing. Possible future therapies include tocilizumab, denosumab and drugs targeting nerve growth factor and its receptor TrkA.

Pharmacology of modality-specific transient receptor potential vanilloid-1 antagonists that do not alter body temperature

The transient receptor potential vanilloid-1 (TRPV1) channel is involved in the development and maintenance of pain and participates in the regulation of temperature. The channel is activated by diverse agents, including capsaicin, noxious heat (≥ 43°C), acidic pH (< 6), and endogenous lipids including N-arachidonoyl dopamine (NADA). Antagonists that block all modes of TRPV1 activation elicit hyperthermia. To identify efficacious TRPV1 antagonists that do not affect temperature antagonists representing multiple TRPV1 pharmacophores were evaluated at recombinant rat and human TRPV1 channels with Ca(2+) flux assays, and two classes of antagonists were identified based on their differential ability to inhibit acid activation. Although both classes of antagonists completely blocked capsaicin- and NADA-induced activation of TRPV1, select compounds only partially inhibited activation of the channel by protons. Electrophysiology and calcitonin gene-related peptide release studies confirmed the differential pharmacology of these antagonists at native TRPV1 channels in the rat. Comparison of the in vitro pharmacological properties of these TRPV1 antagonists with their in vivo effects on core body temperature confirms and expands earlier observations that acid-sparing TRPV1 antagonists do not significantly increase core body temperature. Although both classes of compounds elicit equivalent analgesia in a rat model of knee joint pain, the acid-sparing antagonist tested is not effective in a mouse model of bone cancer pain.

A novel animal model for bone metastasis in human lung cancer

Metastases account for 90% of lung cancer mortalities, frequently target the skeleton and lead to rapid deterioration in quality of life. The molecular mechanism underlying bone metastases is largely unknown. Development of xenograft mouse models, such as the severe combined immunodeficient (SCID) CB-17 mouse and the non-obese diabetic (NOD)/SCID mouse, both of which lack functional B- and T-cells and are able to host allogeneic or xenogeneic tumor cells, has made great contributions in this area. However, residual natural killer (NK) cells in these models are able to significantly modify local tumor growth and metastasis. Treatment with anti-murine IL-2 receptor β chain Ab (TM-β1) antibody can abrogate NK cell activity in vivo; however, the antibody treatment may result in unexpected effects and the stability is hard to control. To overcome these shortcomings, we evaluated xenografts in NOD-scid IL2Rγ(null) immunodeficient mice that lacked mature T cells, B cells and functional NK cells. We compared the target tissue distribution of the human small cell lung cancer cell lines SBC-5 and SBC-3. Gross necropsy and whole skeletal X-ray film examination of the host mice were conducted 30 days post-tail vein injection. The SBC-5 cells colonized bone and formed lytic lesions. The cells also colonized liver, spleen and, less frequently, the pancreas, ovary and kidney. The SBC-3 cell xenografts formed easily visible tumor foci in the liver, pancreas, ovary/uterus and kidney, but not bone metastases. Our results showed that SBC-5 cells in NOD-scid IL2Rγ(null) immunodeficient mice provide a suitable xenograft model system for bone metastasis of human lung cancer. This novel animal model may therefore be used to study the molecular pathway of bone metastases and to evaluate targets for effective therapies.

Pain and inflammation in women with early-stage breast cancer prior to induction of chemotherapy

CONTEXT

Pain is a commonly experienced and distressing symptom in women with breast cancer (BCA), and recent evidence suggests that immune activation may be associated with pain and other co-occurring symptoms. However, no studies to date have explored the relationships among perceived pain and biomarkers of inflammation in women with early-stage BCA during the initial course of treatment.

OBJECTIVES

The purpose of this research study was to examine the relationships among pro- and anti-inflammatory biomarkers and the presence of pain and other symptoms (anxiety, depression, fatigue, and sleep disorder) prior to induction of chemotherapy.

METHOD

This was a secondary analysis of data that measured perceived symptoms, including the presence of pain and pain interference, and plasma levels of pro- and anti-inflammatory cytokines and C-reactive protein (CRP) in women with early-stage BCA (N = 32) at 1 month postsurgery but prior to induction of chemotherapy.

RESULTS

Women experiencing pain had significantly higher levels of CRP (p < .01), interleukin (IL) 13 (p < .02), and IL-7 (p < .02) and more pain interference (p < .01), depression (p < .01), and sleep disturbance (p < .01) compared to women reporting no pain.

CONCLUSION

The presence of pain during the initial course of treatment in women with early-stage BCA was associated with significantly higher levels of CRP, IL-7, and IL-13, suggesting a potential role of immune activation in perceived pain. Further research to examine the precise effects of these biological factors in modulating pain is needed. Perceived pain was also associated with multiple co-occurring symptoms, and this finding has important implications for symptom management.

Development and psychometric evaluation of the chemotherapy-induced peripheral neuropathy assessment tool

BACKGROUND

Chemotherapy-induced peripheral neuropathy (CIPN) can be a debilitating and dose-limiting adverse effect of chemotherapy. Comprehensive self-report tools for CIPN are needed for research and clinical practice.

OBJECTIVE

The purpose of this psychometric study was to describe the development and evaluate the reliability and validity of a new self-report tool designed to measure CIPN, the Chemotherapy-Induced Peripheral Neuropathy Assessment Tool (CIPNAT).

METHODS

One hundred sixty-seven patients receiving outpatient chemotherapy with paclitaxel, docetaxel, cisplatin, or oxaliplatin completed the CIPNAT. Content validity, convergent validity, discriminant validity, test-retest reliability, and internal consistency reliability were assessed.

RESULTS

Content validity index was very acceptable at 0.95. Convergent validity data were provided by correlation with a measure of the same concept (r = 0.83, P < .001), and differences between contrasting groups (t = 7.66, P < .001) provided evidence of discriminant validity. High test-retest correlations (r = 0.92, P < .001), Cronbach α (α = .95), and significant item-to-total correlations ranging from 0.38 to 0.70 provided evidence of reliability.

CONCLUSIONS

Results provide evidence of the validity and reliability of the CIPNAT, which can be used for comprehensive assessment of CIPN.

IMPLICATIONS FOR PRACTICE

Use of the CIPNAT in research may lead to a better understanding of CIPN and guide nurses in developing and testing of interventions to relieve suffering and enhance quality of life for patients with CIPN.

Preventive or late administration of anti-NGF therapy attenuates tumor-induced nerve sprouting, neuroma formation, and cancer pain

Early, preemptive blockade of nerve growth factor (NGF)/tropomyosin receptor kinase A (TrkA) attenuates tumor-induced nerve sprouting and bone cancer pain. A critical unanswered question is whether late blockade of NGF/TrkA can attenuate cancer pain once NGF-induced nerve sprouting and neuroma formation has occurred. By means of a mouse model of prostate cancer-induced bone pain, anti-NGF was either administered preemptively at day 14 after tumor injection when nerve sprouting had yet to occur, or late at day 35, when extensive nerve sprouting had occurred. Animals were humanely killed at day 70 when, in vehicle-treated animals, significant nerve sprouting and neuroma formation was present in the tumor-bearing bone. Although preemptive and sustained administration (days 14-70) of anti-NGF more rapidly attenuated bone cancer nociceptive behaviors than late and sustained administration (days 35-70), by day 70 after tumor injection, both preemptive and late administration of anti-NGF significantly reduced nociceptive behaviors, sensory and sympathetic nerve sprouting, and neuroma formation. In this model, as in most cancers, the individual cancer cell colonies have a limited half-life because they are constantly proliferating, metastasizing, and undergoing necrosis as the parent cancer cell colony outgrows its blood supply. Similarly, the sensory and sympathetic nerve fibers that innervate the tumor undergo sprouting at the viable/leading edge of the parent tumor, degenerate as the parent cancer cell colony becomes necrotic, and resprout in the viable, newly formed daughter cell colonies. These results suggest that preemptive or late-stage blockade of NGF/TrkA can attenuate nerve sprouting and cancer pain.

[Management of painful bone metastases]

Bone metastases are frequently symptomatic. The pain is specific due to its pathophysiology, characteristics and treatment. Conventional antalgic pain management may be insufficient and management should be multifacetted, global and multidisciplinary. Interventional radiology procedures widen the range of possible antalgic therapies. Their role in the management of patients should be defined by a multidisciplinary team on a case-by-case review, based on the patient's symptoms and fracture risk. Additional scientific validation of the effectiveness of such therapies is needed. Recommendations on the role of interventional radiology procedures in the management of patients with symptomatic bone metastases are needed to standardize the different practices and increase the role of interventional radiology in the management of symptomatic bone metastases at the national level. Implementation of the cancer 2009-2012 project could facilitate the availability of these therapies to patients with cancer pain.

Pharmacological treatment of neuropathic cancer pain: a comprehensive review of the current literature

Neuropathic cancer pain (NCP), commonly encountered in clinical practice, may be cancer-related, namely resulting from nervous system tumor invasion, surgical nerve damage during tumor removal, radiation-induced nerve damage and chemotherapy-related neuropathy, or may be of benign origin, unrelated to cancer. A neuropathic component is evident in about 1/3 of cancer pain cases. Although from a pathophysiological perspective NCP may differ from chronic neuropathic pain (NP), such as noncancer-related pain, clinical practice, and limited publications have shown that these two pain entities may share some treatment modalities. For example, co-analgesics have been well integrated into cancer pain-management strategies and are often used as First-Line options for the treatment of NCP. These drugs, including antidepressants and anticonvulsants, are recommended by evidence-based guidelines, whereas, others such as lidocaine patch 5%, are supported by randomized, controlled, clinical data and are included in guidelines for restricted conditions treatment. The vast majority of these drugs have already been proven useful in the management of benign NP syndromes. Treatment decisions for patients with NP can be difficult. The intrinsic difficulties in performing randomized controlled trials in cancer pain have traditionally justified the acceptance of drugs already known to be effective in benign NP for the management of malignant NP, despite the lack of relevant high quality data. Interest in NCP mechanisms and pharmacotherapy has increased, resulting in significant mechanism-based treatment advances for the future. In this comprehensive review, we present the latest knowledge regarding NCP pharmacological management.